1. Field of the Invention
The present invention concerns a turbojet-engine thrust-reverser, preferably with a high bypass ratio.
2. Description of the Related Art
Turbojet-engines include a primary exhaust duct through which so-called hot propulsive gas flows and an annular duct coaxial with the primary duct through which so-called cold propulsive gas flows. The cold gas flow constitutes the exhaust of a fan located at the intake of the turbojet engine and is a secondary, i.e., bypass flow of the engine. Thrust reversal of the engine is achieved by implementing, mostly or entirely, deflection of the secondary, i.e., bypass flow, in particular when the bypass ratio (i.e., the ratio of bypass to primary exhaust flow) is high.
As regards such applications, it is known to use displaceable components, i.e., baffles or deflectors, which in their extended position can form a continuous annular sub-assembly sealing the bypass duct to deflect the bypass flow and to orient the flow stream while providing thrust reversal. On the other hand, in the forward-thrust mode, the baffles must be retracted and masked while leaving the bypass duct clear for the bypass flow. In some known thrust-reverser models, the baffles are retracted into the radial outer wall of the bypass duct.
Other solutions retract the baffles to the level of the radial inner wall of the bypass duct or enclosing wall, also called the primary cowling, of the inner or central engine. Designs of this type are disclosed in particular in the French patent document A 1,479,131. Various improvements have been proposed in the French patent documents A 2,625,261 and A 2,650,861.
Such designs are especially useful for high bypass ratios and when the radial outer wall of the bypass duct is shorter than the radial inner wall of the bypass duct.
In such a case and according to U.S. Pat. No. 3,280,561 and French patent 2,625,261, the displaceable components, i.e., the baffles, are mounted on the stationary or fixed structure enclosing the engine's gas generator using fixed pivots. The hinge allowing the baffles to pivot may be mounted on the downstream side of the baffle; however, in this case the baffle displacement entails a bypass-duct blocking position which hampers engine operation. Safety problems remain because the baffles are not self-closing. In the event the hinge is placed upstream of the baffle, the jet deflection is implemented by the baffles' outside surfaces; but, this feature precludes optimizing configurations for both reversed and forward thrust modes. Another major drawback of the latter design is the need to use a spoiler or retractable deflector, subject to high stresses, at the ends of the baffles of sufficient size to assure effectiveness.
U.S. Pat. No. 4,216,923 shows a synchronized baffle drive system which requires fitting the assembly with complex and mutually parallel guide and drive means.
Thus, problems remain, taking into account aircraft installation conditions and weight savings, in matching a thrust reverser of this kind to a high bypass-ratio powerplant, while avoiding increasing engine bulk, in particular its outside diameter, and decreasing the ground clearance. Moreover, it must be possible to mount the thrust reverser on a turbojet-engine cowling with the bypass ratio being at least 4. The thrust reverser also must effectively permit the required thrust-reversal performance, and, when in the forward-thrust mode, must provide an aerodynamically continuous inner wall without introducing flow-degrading perturbations.